Heterogeneous Extended Langmuir Model with Multiregion Surfaces for Adsorption of Mixtures

Bai, Rui

doi:10.1006/jcis.2002.8546

Cited by 7 publications

(13 citation statements)

References 21 publications

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“…As in the previous work, , we assume that the pure-component parameters for component A are the same on both regions. For more regions, this assumption remains.…”

Section: Theorymentioning

confidence: 99%

“…In the last two years, Bai and Yang , have proposed a multiregion adsorption (MRA) theory which was used to improve a number of mixture adsorption models while maintaining thermodynamic consistence for each model. The basis of MRA is the heterogeneity of adsorption surfaces for all real adsorbents.…”

Section: Introductionmentioning

confidence: 99%

“…The MRA theory has been successfully applied to the EL model 19 and the HEL model . Compared to the respective original models, the modified models showed similar prediction results for ideal mixtures or mixtures containing like components.…”

Section: Introductionmentioning

confidence: 99%

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Improved Multisite Langmuir Model for Mixture Adsorption Using Multiregion Adsorption Theory

2003

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Prediction of mixed gas adsorption by the multisite Langmuir (MSL) theory is significantly improved by incorporating the multiregion adsorption (MRA) theory. The new model, called the multiregion multisite Langmuir (MR-MSL) model, is thermodynamically consistent. MR-MSL uses the same pure-component isotherm parameters as MSL does, and no new parameters are introduced. Eight binary systems and one ternary system are used to test the MR-MSL model. For systems containing like components (such as mixtures of hydrocarbons and that of O2 + N2), MR-MSL yielded only minor improvements over MSL. This is true regardless of the magnitude of the differences in the pure-component MSL parameters among different components. For highly nonideal mixtures, MR-MSL results in very substantial improvements. It is also capable of predicting the azeotropic behavior of the adsorption of CO 2 + C3H8 on H-mordenite and the correct azeotropic compositions. For such systems, it is also shown that surface heterogeneity needs to be considered.

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“…As in the previous work, , we assume that the pure-component parameters for component A are the same on both regions. For more regions, this assumption remains.…”

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improved Multisite Langmuir Model for Mixture Adsorption Using Multiregion Adsorption Theory

2003

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“…an observed decrease in x with increasing W at a given value of A) associated with significant parameter variations upon changes in W ( Leyva-Ramos et al 1999;Voice et al 1983;Voice and Weber 1985;Wu et al 2006). Changes in the adsorbate concentration are also an important factor in the observed variations of traditionally defined equilibrium parameters (Bai and Yang 2002;Cseh and Benz 1998;Zuyi and Taiwei 2000). Mura-Galelli et al (1991) reported that "the Langmuir equation does not accurately describe the experiment over the entire adsorption domain".…”

Section: Introductionmentioning

confidence: 97%

An Ion Adsorption Model Related to the Change in the Standard Chemical Potential of Adsorption Reactions

2011

Adsorption Science & Technology

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A simple model is proposed for the prediction of equilibrium ion adsorption in liquid/solid systems. The establishment of the model was based on the assumption that the change in the standard chemical potential of the adsorption system should be zero if ion adsorption taking place spontaneously at a constant temperature is purely a thermodynamic process in which, driven by the electrochemical potentials, the ions move between liquid and solid phases without changing their chemical nature. Experiments have been conducted to test this assumption using the adsorption of Zn 2+ , Cd 2+ and K + ions from aqueous solutions onto swelling vermiculite, natural zeolite and synthetic zeolite. The results showed that the proposed model fitted the experimental data well. This study provides evidence that, under the conditions employed, ion adsorption reactions are essentially physical processes and the change in the standard chemical potential of the adsorption reaction is negligible.

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“…Just like in VLE, this means the selectivity S 12 = ( x 1 / y 1 )/( x 2 / y 2 ) = 1.0 at this point. Although less known and less understood than VLE azeotropic behavior, adsorption azeotropic behavior appears to be a common phenomenon in gas–solid adsorption equilibria. − …”

Section: Introductionmentioning

confidence: 99%

Theoretical Analysis of the Necessary and Sufficient Conditions for the Formation of Adsorption Azeotropes in Binary Gas Mixtures

2021

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This work theoretically assessed the necessary and sufficient conditions for the formation of an adsorption azeotrope in a binary gas mixture when this mixture exhibits either intersecting or nonintersecting single gas isotherms. The thermodynamically consistent dual process Langmuir (DPL) model with equal component i saturation capacities q i,j s on site j and the general DPL model with nonequal q i,j s on site j were used for this purpose. Analytical expressions derived for both DPL models, in terms of the single gas isotherm DPL model parameters, were used to find examples or to determine theoretically when an adsorption azeotrope forms in a binary gas mixture for both intersecting and nonintersecting single gas isotherms. For the general DPL model, it was determined that neither necessary nor sufficient conditions exist for the formation of an adsorption azeotrope in a binary gas mixture. This means that an adsorption azeotrope can form irrespective of whether the corresponding single gas isotherms intersect or not. For the thermodynamically consistent DPL model, it was determined that the intersection of the single gas isotherms is a sufficient condition for the formation of an adsorption azeotrope in a binary gas mixture, but it is not a necessary condition. This means that intersecting single gas isotherms guarantee the formation of an adsorption azeotrope in the corresponding binary gas mixture, while nonintersecting single gas isotherms can also result in the formation of an adsorption azeotrope in the corresponding binary gas mixture. Overall, this analysis provides a well-posed resolution to the question of necessity and sufficiency for the formation of adsorption azeotropes in binary gas mixtures and the intersection of their corresponding single gas isotherms based on two physically sound formulations of the very popular DPL model.

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Heterogeneous Extended Langmuir Model with Multiregion Surfaces for Adsorption of Mixtures

Cited by 7 publications

References 21 publications

Improved Multisite Langmuir Model for Mixture Adsorption Using Multiregion Adsorption Theory

Improved Multisite Langmuir Model for Mixture Adsorption Using Multiregion Adsorption Theory

An Ion Adsorption Model Related to the Change in the Standard Chemical Potential of Adsorption Reactions

Theoretical Analysis of the Necessary and Sufficient Conditions for the Formation of Adsorption Azeotropes in Binary Gas Mixtures

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